I read a few books about Lincoln. It was said that his chronic "melancholy" (depression) allowed him to see the world as others didn't, thus he almost solely saw the danger in the "Missouri Compromise" (that the South wanted to colonize S America and West as half slave states) and was willing to act upon in in decisive fashion.

I guess now that I've read this, I've also learned that Lincoln's path to the Presidency was predicated on one important thing...the ability/strength to quit Speed and wed Mary Todd!